NEW YORK — Over the final innings of Toronto’s 12-1 rout of the Mets on Wednesday, Zack Wheeler wisely thought better of watching the performance on the field. Wheeler, who allowed the first half of the Blue Jays’ dozen runs in just four-plus frames, had already had enough time in the clubhouse to diagnose his flaws. And so he spent the rest of the game searching for a solution.

With first baseman Adrián González by his side, Wheeler dissected video of Roger Clemens and Curt Schilling, with an eye on learning the art of the split-finger fastball.

Until two starts ago, Wheeler didn’t throw a splitter. Now, he sees it as a way of fixing what ails him.

The plan for Wheeler entering the season was to get into more advantage counts and to simply let his stuff play from there. It made sense: Last season, nobody in baseball saw starker divisions based off the first pitch of a plate appearance. When Wheeler got ahead 0-1, he was dominant; when...